The present invention relates to novel organosilicon compounds and to a method for their preparation. Specifically, this invention relates to novel branched organosilicon compounds having silalkylenesiloxane units, and to a method for their preparation.
Organosilicon compounds having silalkylenesiloxane units of the formula: ##STR1## where R is a monovalent hydrocarbon group, and n is a positive integer have been disclosed and are known to be resistant to molecular chain scission by ionic substances such as acids or alkalis compared to other known diorganopolysiloxanes. Methods of making these organosilicon compounds having silalkylenesiloxane units by ring-opening polymerization of cyclic silalkylenesiloxanes have been proposed by Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4,739-744, April, 1971, and are disclosed in Japanese Patent Application Laid-Open No. 4-65428 (65,428/1992), and in Japanese Patent Application Laid-Open No. 4-65429 (65,429/1992).
However, in the methods described above, cyclic silalkylenesiloxanes such as 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane are prepared in advance, and then subjected to ring-opening polymerization. Thus the polymer compounds obtained in the above methods are linear polymer compounds. There has been no disclosure of branched organosilicon compounds having silalkylenesiloxane units.